Non-contact measurement of pulse wave in rats using an RGB camera

In this paper, we propose a measurement method using an RGB camera to non-invasively capture the pulse wave in rats. Most attempts to capture biological information from an animal, such as pulse wave, requires contact that is invasive and influence the animal. In this study, we attempt to apply remote photoplethysmography (rPPG) to rats. Our rPPG method uses an RGB camera to detect the change of hemoglobin amount in the skin and derives pulse waves. First, we removed body hair and captured an image of the skin in the hair removed area. The rat's pulse rate is approximately 300 beats per minute, which is much faster than the pulse rate of a human; then we captured video of the skin at a frame rate of 250 frames per second (fps). As a result, pulse waves were obtained from the image signals of the skin with signal processing. Next, we focused on the sole of rats whose skin is directly visible, and we tried to detect the pulse wave from the sole. We made a novel rat observation apparatus, where the cage floor is made of a transparent acrylic plate, and images of rate roles were captured through the acrylic plate by setting the RGB camera under the cage. As a result, we were able to measure pulse waves in rats by a non-contact, non-invasive, unrestrained, and no anesthesia approach. We also demonstrated the effectiveness of the proposed method we could successfully detecting arrhythmia caused by fear (fox smell).